Is it Too Late to Apply Nitrogen Fertilizer to Warm Season Grasses?


nitrogen fertilizer

The simple answer if you are reading this in late August or early September is “No.”  This decision is based on several different factors.  A general rule is to apply the last nitrogen fertilizer to a lawn that contains warm-season turfgrasses two months before the first frost. Unless you live in the deep south, the last application of a fertilizer that contains a high amount of nitrogen would be September 15 at the latest. If you live in the more northern areas, you run the risk of turf damage and lawn disease development if nitrogen is applied after September 1st.  Of course, these are based on averages, so there is a little “wiggle” room, but not much.


Applying Nitrogen Fertilizer to Warm Season Grasses

Centipede, St. Augustine, Hybrid Bermuda and Zoysia grass are the most common warm season grasses and they usually go dormant in the late fall.  Applying a high rate of nitrogen after the middle of September for the more moderate warm-season areas will increase the shoot and leaf growth while the plant is slowing its growth.

It is important that these grasses have a chance of “harden-off” before going dormant.  If pushed to grow, the tender new growth is more susceptible to freeze damage.  These succulent shoots are prone to being attacked by a common cool-season disease called Large Patch.

Another problem with fertilizing later in the fall is that it may increase the number of cool-season weeds that germinate. Weeds like henbit, common chickweed and Shepherd’s Purse are considered winter annuals and will grow and spread while the desired grasses have slowed down growing.

Determining Nitrogen, Phosphorus and Potassium in Fertilizer

The three numbers on a bag of fertilizer indicate the percentage by weight of nitrogen, phosphorus and potassium in the bag. The number one nutrient needed by turf is nitrogen. Here is a chart that provides the amount of nitrogen each turf type needs for the entire growing season.

Warm Season Grass#’s of Nitrogen Per Year
Hybrid Bermuda5 to 6 lbs.
Common Bermuda4 to 5 lbs.
Centipede Bermuda1 to 2 lbs.
St. Augustine grass (sun)3 to 4 lbs.
St. Augustine grass (shade)1 to 2 lbs.
Zoysia grass3 to 4 lbs.


If you haven’t applied the recommended amount of nitrogen to your lawn this year, don’t try to catch up now.  In regards to the other two nutrients, phosphorus and potassium, they are required, but they are usually found in an abundant amount in the soil. The only way to tell if the lawn needs either of these two nutrients is to have your soil tested.  Most cooperative extension services offer this service at a low fee of less than $25.00 per sample.

If you live within the area that has a first frost date of mid-October, try to fertilize between Labor Day and the end of September, depending whether you are in the northern or southern parts of that zone. If you are not sure, contact your neighborhood lawn care professional at Spring-Green.

The Best Time to Aerate Your Lawn, for Cool and Warm Season Grasses

core aerator used by a Spring-Green technician

September is here and the amount of sunlight is becoming less and less each day. Less sunlight means that the leaves on trees will start to show their fall colors, summer weeds will begin to slow down growing and another summer is coming to a close. Early fall lawn projects are on homeowners’ minds, and many are wondering if this is the best time to aerate their lawns.

Aerating Your Lawn in the Fall Works for Cool Season Grasses

For cool-season grasses, this is the time of year when the top growth slows down and the root growth increases. Fall is the time when these grasses naturally “repair” the damage that was caused by the stresses of summer. Heat and a lack of rain have taken their toll on cool-season lawns. Insect and disease outbreaks add to the damage level and have left many lawns in a sorry shape for the fall.

In my 37+ years in lawn care, I have always been amazed at the recuperative ability of turfgrasses to recover from these stresses. Even though they can come back, one of the most important things you can do to help a cool-season lawn recover is to core aerate to increase rooting and the overall health of the lawn. It is also a good idea to overseed the lawn to help it fill in even faster. By opening up the lawn, more air, water and nutrients can easily reach the root zone. The cores or plugs of soil that are left behind will breakdown and incorporate into the thatch layer. It is the microorganisms in the soil that feed and the thatch to lessen its impact on the lawn.


When Is the Best Time to Aerate Warm Season Grasses?

For those of you that have warm-season grasses, the best time to aerate your lawn is in early summer. If you aerate the lawns right now, they won’t be harmed, but the benefits are much less.

When Is the Best Time to Add Nitrogen Fertilizer?

If you plan to apply an application of nitrogen to your warm-season lawn one more time this year, be sure to do so by the end of September. Stimulating new growth in October or November can be detrimental to the lawn if an early frost hits the area. Too much nitrogen in the fall can also lead to an increase in disease activity the following spring.

Before we know it, leaves are going to begin to fall. There are a number of fall lawn and landscape projects that are coming up as the year moves on. I will be discussing those in future blog posts. Enjoy the last of the summer warmth while you can.

Core aeration is just one of the services Spring-Green offers to help homeowners prepare their lawns for winter. Contact your local Spring-Green for a free estimate of your lawn’s unique needs.

How Grass Grows: Seed Heads, Flowers and Fertilizer

grass with seed heads

I recently attend a training class on identifying grasses and grassy weeds led by Dr. Tom Voigt, Associate Professor and Extension Turfgrass Specialist from the University of Illinois. Even though I knew all the grasses and how to go about identifying them, I am usually always able to learn something new at these events—in this case, I took away valuable information on grass seed heads and flowers, as well as how grass grows.

Flowering and Seed Heads

All grasses produce flowers and a seed head. If you live in cool-season turfgrass areas, this is the time of year when these grasses are “going to seed.” If you live in the South, those grasses will begin seeding around this time. Producing flowers and seed heads is part of the normal growth process of just about every plant.

Dr. Voigt said that as your grass grows, one way to reduce the amount of flowers and seed heads that are produced is to fertilize the lawn with nitrogen. The nitrogen will stimulate more leaf and shoot growth, keeping the plant less likely to produce as many seed heads. The concept is similar to fertilizing tomato plants. If a tomato is fed a high amount of nitrogen, the plant will get huge, but there will be very few tomatoes on it. All the energy is going into growing leaves and not much into fruit production.

How Does Grass Grow?

Another thing I learned is how grass grows. I was always under the assumption that grass grows up from the tip of the leaf blade. In actuality, the grass pushes the blades up from the crown of the plant. That is where the meristematic cells are located. The meristematic cells are the growth cells. When I think about it, it makes perfect sense that grass grows up from the crown and not from the tip of the blade. If it did, then when the lawn is mowed, the grass would not grow anymore.

When the flower heads or seed heads are cut off, the stalk that is left behind will turn straw-colored as it dies. If there are an abundance of flower/seed heads that have been cut off, the lawn will take on a sort of ragged, unkempt appearance. Producing the flower/seed heads also uses up a good deal of energy from the plant, and it takes time for it to recover and grow new leaves. It will come back, so try to be patient!

At Spring-Green, we can help you with just about any lawn care need—from fertilization and weed control to insect control and more, we’re here to help you have a healthy, beautiful lawn!